The present invention relates to a 1-chip type semiconductor integrated circuit (IC) device in which a plurality of functional circuits having different functions are integrated.
In the field of personal computers, mobile phones, game devices, etc. which use semiconductor devices, there is a great demand for an increase in the number of functions and a reduction in size and cost.
As the number of functions increases, the structure of the system becomes complex. As the system comes complex, a semiconductor device having various functions is required and a memory having a large capacity is needed. Thus, the number of single-unit semiconductor devices necessary for constructing the system increases.
There is a tendency that a greater number of functions are integrated in a 1-chip semiconductor device and the size of the 1-chip semiconductor device decreases. The same applies to a memory device. The capacity of a 1-chip memory increases while the size of the 1-chip memory decreases.
However, the increase in the number of functions is rapid while the decrease in size is slow.
Recently, a multi-chip module wherein semiconductor chips with different functions are packed has been developed, thereby advancing the reduction in size of the semiconductor product. In the multi-chip module, good-quality semiconductor chips are packed. As compared to the manufacture of a single-unit semiconductor device, an assembly step for assembling good-quality semiconductor chips needs to be provided. In the assembly step, if a defect in connection occurs, the produced device may become defective even if good-quality semiconductor chips are contained, and the reduction in manufacturing cost is prevented. This being the case, it cannot be said that the multi-chip module meets the demand for reduction in cost.
Under the circumstances, a so-called xe2x80x9csystem-on-siliconexe2x80x9d technique, in which a plurality of functional circuits having different functions are integrated into only one semiconductor chip, has recently been developed. It is possible that the system-on-silicon technique will meet all requirements for the increase in the number of functions and the reduction in size and cost.
A semiconductor device according to an aspect of the present invention comprises: a semiconductor substrate of a first conductivity type; at least one first well of a second conductivity type formed in the semiconductor substrate; and at least one second well of the first conductivity type formed in at least one first well, wherein the semiconductor device is composed of semiconductor circuits each formed in at least one first well and at least one second well.